fun main(args:Array<String>){
    val countryCapitals=mapOf(
"china" to "北京",
"USA" to "华盛顿",
"Japan" to "东京"
    )
// 访问元素
println("中国的首都是${countryCapitals["china"]}")
println("包含法国吗?${countryCapitals.containsKey("france")}")
// 遍历键值对
println("\n国家首都列表")
countryCapitals.forEach{
    (country,capital)->println("${country}的首都是${capital}")
}
}